<template>
  <div>
    <p>请选择你要购买的书籍</p>
    <ul>
      <li v-for="(item,index) in arr" :key="index">{{ item.name }} <button @click="buyBook(index+1)">买书</button></li>
    </ul>
    <table border="1" width="500" cellspacing="0">
      <tr v-for="(item,index) in arr" :key="index">
        <th>{{ index + 1 }}</th>
        <th>{{ item.name }}</th>
        <th>{{ item.price }}</th>
        <th>{{ item.count }}</th>
        <th>合计{{ item.price * item.count }}</th>
      </tr>
    </table>
    <p>总价格为:{{ sumP }}</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      arr: [
        {
          name: "水浒传",
          price: 107,
          count: 0,
        },
        {
          name: "西游记",
          price: 192,
          count: 0,
        },
        {
          name: "三国演义",
          price: 219,
          count: 0,
        },
        {
          name: "红楼梦",
          price: 178,
          count: 0,
        },
      ],
    };
  },
  methods:{
    buyBook(id){
      this.arr[id - 1].count+=1
    }
  },
  computed : {
    sumP(){
      return this.arr.reduce((sum,item) => sum+=item.price*item.count ,0)
    }
  }
};
</script>